Lead product



Patented Sept. 11, 1962 Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Mar. 28, 1960, Ser. No. 17,789 3 Claims. (Cl. 75211) This invention relates to a new form or new type of lead product, and more particularly, to an improved method for forming solid lead shapes.

Generally, the fabrication of solid shapes or stocks of metals from subdivided supplies of the desired metal, are generally well known. In the main, however, these techniques have involved the pressing of shapes followed by sintering operations at or about the melting point of the metal or alloy involved. In some cases, particularly with alloy, sintering temperatures employed are below the melting point of the alloy. Although powder metallurgy techniques are fairly well established for many metals, they have not been extensively used for predominantly lead shapes, that is, shapes made essentially of lead metal.

The principal object of the present invention is to provide a new and improved process for the fabrication of finely divided or subdivided lead powders into ultimate stock shapes. More particularly, an object of the invention is to provide method of preparation of lead stock shapes from subdivided lead metals, characterized by particularly facile formation of said shapes. Yet another object is to provide ultimate shapes wherein the physical properties can be readily controlled, i.e., with respect to density, strength, flexibility, and other attributes of the ultimate solid shape. Still another object of certain embodiments of the invention is to provide a new technique whereby lead shapes having controlled porosity are established. Yet an additional object of certain species of the invention is to provide a new form of lead metal of relatively thin cross section, having controlled porosity, thereby providing a new and useful structure. Other objects will appear hereinafter.

The present invention, in its most general form, comprises subjecting a mixture of subdivided essentially lead metal powder with a minor quantity of a liquid lead organo compound present therein, to a mechanical forming operation. This provides a lead shape having the lead organo component interspersed or distributed in said apparently entirely solid shape. The so-formed initial shape is then further treated to destroy or decompose the organometallic component therein. Typical means or methods of accomplishing said decomposition involve heating the shape at an elevated temperature, above the decomposition temperature of the lead organo liquid component and for a sufiicient period of time to decompose substantially all of said component. Another mode of accomplishing the necessary decomposition is to treat the lead shape, with the lead organo compound therein, with a liquid reagent, for such period as required to chemically and relatively selectively react with all of the organometallic components. These typical treatment procedures result in the deposition of lead from the said lead organometal component, or the conversion of the lead organo compound to an inorganic compound.

Although in all forms of the invention, the lead organo compound provided and present distributed in the solid appearing shape formed in the forming operation is disintegrated or decomposed, nevertheless the presence of this minor quantity of a component during the forming operation provides a surprising and beneficial effect on the forming as will appear in more detail hereinafter. This effect is evidenced by the lower forming pressures required in certain embodiments, or in the ease, generally,

of conducting said forming operations. Further, in certain embodiments, the presence of the liquid lead organo compound in the formed shape, prior. to decomposition thereof, makes possible, or facilitates the generation of controlled porosity in the final lead product.

The lead solids employed in the process can vary appreciably in size and source characteristics. As apparent hereinafter, the lead powders employed can be generated by chemical reaction means, or, alternatively can be generated from massive lead by essentially mechanical comminuting means. As described hereinafter, the physical form of the individual particles will vary according to the preparatory source for said feed material. The particular size definition of a powder employed in any individual embodiment is not highly critical. In some cases, a gross product, ie that which is obtained as is from a conrminuting operation, either chemical or physical, is employed without any size assorting. In other instances, it is found highly desirable to employ a particular screen fraction. With respect to the size of the maximum size particles of any particular feed material, in virtually all instances all the particles are preferablysmaller than about 0.1 inch in maximum orthographic projection. In other 'WOI'dS, in practically all instances, virtually all the particles of a lead powder will pass a N o. '8 screen of the US. sieve series, having openings of 0.0937 inch. It is more common however, that the average particle sizes will be considerably lower than this maximum preferred size. In most cases, at least about of the powdersupply will pass a No. 10 screen, and be retained on a No. 200 screen, the latter having openings of 0.0029 inch. More specifically, in practically all cases the preferred size distribution of the lead particles is such that from about 70 to weight percent is retained on a No. 200 screen. In some application a more restricted screen fraction is employed and will provide greater strength when desired. A typical preferred screen fraction is that portion passing a mesh screen and being retained on a No. 325 screen, and for certain purposes, a fraction passing a No. 325 screen, is used.

The particular identity of the lead organo liquid compound Which is provided as a component of the original powder mixture is not highly critical, but such a component can be selected from a' substantial variety of individual compounds, or can be a mixture of compounds, tetraethyllead being a readily available and a relatively low priced material, is the most common lead organo compound employed. However, as will be clear from the examples hereinafter, numerous other lead organometallic products can be provided. Illustratively, these include tert-butyl trimethyllead, ethyltriphenyl lead, tetraamyl lead, tetrahexadecyl lead, tetramethyllead, tetra decyl lead, amyl triphenyl lead, butyl triisobutyl lead, butyl triethyl lead, butyl triphenyllead, butyl diethyl methyl lead, dimethylethyl isoamyl lead, and numerous other individual components. In some instances, the lead organo compounds are solid materials at ambient temperatures, but have sufiiciently low melting points that by carrying out the forming operation at only moderately elevated temperatures, a liquid phase is established. Organolead compounds having a halogen substitutent can be employed, examples of these being triethyllead chloride and others. Other organolead compounds wherein an anion other than a halide is present in the molecule are suitable, a typical example of such being triethyllead monoethyl oxalate, tridodecyl lead nitrate, tripropyl lead methyl sulfonamide, and triethyl lead sulfide. Generally, the organolead compounds having certain inorganic substituents, as described above, are not highly desirable, because these materials are relatively stable and in addition have higher melting points than the lead tetraorgano compounds, and in particular the lead tetraalkyl compounds.

.The particular proportions of lead organo compounds employed will depend upon the ultimate properties required and to some extent on the density of the lead organometallic component. Another factor influencing the quantity of the lead organo component originally present is the forming techniques to be employed. The majority of embodiments employ a concentration of about 1 to Weight percent of the lead organo compound, in some instances even higher, and a preferred range being from about 1 to 5 weight percent.

A variety of forming techniques are readily available as the first step of the process. Typical modes of operating include the extrusion of the first shape, by forcing the mixture of lead powder and lead organo compounds through a die under pressure. Another typical type of forming includes pressing a discrete quantity of the mixture in a form such as a bar mold, or in a die mold conforming in configuration to an ultimate part. Another mode of forming the shapes involves providing a continuously fed layer of the mixture to a pair, or a plurality of pairs, of turning rolls similar generally to metal working rolls. Combinations of these forming techniques are eminently suitable. Thus, when desired, a shape can be prepared by forcing the mixture through a die having an elongated configuration corresponding to, roughly, the ultimate stock shape desired. This would provide, for example, a strip, bar, rod, or similar stock shape, but not having the desired ultimate dimensions. This preliminary stock shape is then further mechanically formed by passing through an appropniate set of rollers for additional cross sectional area reduction. The mechanical forming operation employed, and most of the steps of the various embodiments of the process, are carried out under hygienically controlled conditions. By this is meant that exposure of operating personnel to atmosphere directly surrounding the work material is avoided until processing is entirely completed. This presents any hazard or toxicological disadvantage associated with the organolead compounds present in the processing mix or work pieces.

The degradation or decomposition of the organolead compound which is present, interspersed in the lead shape resultant from the mechanical shaping operation, can be accomplished by several methods. As already indicated, heat-ing to provide a thermal decomposition of the component is eminently satisfactory. An additional type of treatment involves the treating with a chemical reagent for chemical reaction thereof. Typical reactants for this purpose are strongly oxidizing agents, such as aqueous solutions of potassium permanganate, halogens, and the like. To a certain degree some of the degrading operations to destroy the lead organo liquid component of the shapes, is accompanied by a vaporization thereof with no change. In these instances some mode of recovery thereof is highly desirable. The vaporization which occurs, for example, conjointly with a thermal decomposition operation, is sometimes expedited by the use of the flow of an inert gas past the work piece. In certain modes of operation, the inert gas can provide removal from the work piece of almost all of the lead organo compound as such, thus allowing recovery. It will be clear that by adjustment of the conditions to cause adjustment of the proportion of the lead organo component by decomposition, or reaction, and actual removal by vaporizing, the quantity of additional lead formed within the work shape can be adjusted. Accordingly, this variable permits a high degree of control of the physical properties of the ultimate shape with regard to porosity, and to a limited extent, the density thereof.

The mode of carrying out the several embodiments of the operation of the process will be more readily understood from the working examples given hereinafter.

Example I A supply of commercial lead dust was obtained and chemically mixed with liquid tetraethyllead in the proportions of about 10 weight percent thereof. The lead powder employed had been prepared by mechanical comminution, such as by melting the lead and atomizing with an inert gas jet. The particles were fine powder particles, ranging in size from about 0.005 to about 0.05 inch in maximum dimensions.

A portion of the mixture thus formed was charged to a processing barrel, fitted with a ram tightly sliding therein, and having a die closure at one end, having a die opening providing only about of the cross sectional area of the chamber proper. A pressure was applied, by the ram, on the charge thereto, and it resulted in forcing through the die a rod-like product, which had only about 1 weight percent tetraethyllead adherent to and interspersed therein. The rest of the tetraethyllead originally present was discharged as a discrete liquid phase which was readily separated from the rod-like product.

Portions of this rod-like product are then further passed through rolls to provide a desired ultimate cross sectional configuration.

After achieving the desired cross sectional configuration the shapes are passed through a heating furnace and subjected to a temperature of approximately 200 C. for about /2 hour. A highly dense product is achieved, having greater tensile strength and rigidity than lead which is prepared by solidifying molten lead. The product contains virtually no detectable organic lead component.

Exampie II This example illustrates the preparation of the charge stock for the present process by chemical means. parts of monosodium lead alloy, NaPb, were charged to an autoclave along with about 50 parts of ethyl chloride, this amounting to approximately 75 percent excess ethyl chloride. The mixture was reacted at an autogenous pressure at elevated temperature until the action is terminated as shown by a decrease in temperature and pressure. The product of this reaction was an apparently dry reaction mixture containing about 55 weight percent lead, 24 percent tetraethyllead, and 20 percent sodium chloride. Excess ethyl chloride was vented during the reaction and upon completion of the reaction. The dry granular material resultant was then discharged from the autoclave and immersed in water, then was subjected to steam distillation for a sulficient period of time to remove a large proportion of the tetraethyllead component. The result material is a multiphase mixture of the subdivided lead particles, sodium chloride (largely dissolved in the aqueous phase) and minor quantities of tetraethyllead in usually, the order of several percent, based upon the lead.

Supplies of this mixture, containing about 2 percent tetraethyllead, and, initially 8.6 weight percent water, were subjected to pressure in an extrusion type apparatus, fitted with a die having only of the cross sectional area of the chamber proper. Upon application of the pressure of the order of about 25,000 pounds per square inch on the mixture in the extrusion chamber, a densified, bar-like product is discharged through the die orifice. Analysis of this shape shows only about 0.6 weight percent TEL, with extremely low water content. The bar-like shape can be a cylindrical bar, or, preferably, in the form of a relatively fiat shape, thus providing a shape suitable for use as such, or for subsequent and additional mechanical treatment. The material thus formed is again subjected to an elevated temperature, of about 250 C., for a period of about /2 hour. This completely dries the shape and in addition decomposes the tetraethyllead interspersed in the solid shape. Prior to the thermal treatment, frequently, a rolling operation is provided which can be used to provide the exact ultimate cross sectional configuration desired. The shapes thus produced again are extremely strong, relatively, having tensile strengths of the order of 5,000 pounds per square inch and above, and being quite stifi and sturdy.

The presence of the lead tetraethyl in the initial mixture provides a particularly beneficial effect in the mechanical forming operation, inasmuch as a high degree of lubricity is provided so that the pressure required for operation is appreciably lower than would be essential if no liquid phase is present. Further, as is demonstrated hereinafter, the presence of the lead organo-component interspersed in the ultimate solid shape permits the establishment of desired physical properties.

Example III In this operation, the feed mixture employed is subdivided lead dust with about weight percent tetraethyllead, as in Example I above. However, instead of subjecting this mixture to an extrusion type operation, the mixture is fed to a moving steel metal conveyor belt in a layer of approximately A; inch thick. The belt itself is threaded through a set of forming rolls which process and shape the subdivided solids into a loosely compacted strip shape of approximately of an inch thick. Very little separation of the organolead component is achieved by this initial treating. The so-formed thin shape is rolled, then, further, to a thickness of approximately 0.02 inch. Analysis of the solid thus formed shows that an appreciable quantity of the tetraethyllead is still interspersed in the solid shape. Passage of this thin sheet through a heating furnace, providing a tem- 3 Example IV In this operation the subdivided lead is prepared generally as in Example II, above. However, the reaction mass is not treated to separate very much of the tetraethyllead formed, but, instead, only minor quantities are removed by distillation. The residue, which is further processed as described below, contains, then, about 8 4 weight percent tetraethyllead and somewhat less water component.

Supplies of this mixture are subjected to pressures of the order of 5,000 pounds per square inch in a closed forming chamber. By this is meant that pressure is applied with the minimum quantity or opportunity for discharge of discrete liquid phases. The tetraethyllead content is, however, somewhat reduced to about the order of 3 weight percent. The water content is reduced somewhat further, to about less than 1 weight percent. The rod-like shaped form is relatively brittle, but possesses sufiicient length to permit drawing to a series of stationary reducing dies to provide a desired cross sectional configuration such as wire, strip, or other shapes such as an angle or a channel. In reducing the cross sectional thickness of such shapes, in a series of steps, to the order of about M inch, the tetraethyllead content is further significantly reduced to the order of about 1 weight percent. The tetraethyllead provides a highly beneficial lubricating eifect, as a self generated lubricant, as the shape passes through each reducing die. Upon completion of this treatment, the so-formed shape is passed through a batch of 10 weight percent aqueous solution of potassium permanganate, at boiling temperatures, which selectively reacts with the tetraethyllead on the surface and permeating the shape, and completely converts it to an inorganic form of lead.

1 When the foregoing operations are repeated, but the formed and drawn shapes are treated with other chemical agents for reacting with the organolead present, similar results are provided. Thus, instead of the potassium permanganate, aqueous solutions of chlorine, bromine, iodine can be employed with quite good results. A feature to be avoided in these instances is undue reaction of such strong reagents with the lead metal, which will occur if exposure is unduly prolonged. However, the rapidity of reaction with the organolead component is much greater than reaction with the metallic lead, so appropriate adjustment of times and concentrations of the treating agents is readily made. Sulfuryl chloride is also very advantageously used in some instances. Another elfective reagent is an aqueous solution of sodium hypochlorite.

Example V The procedure of Example IV is repeated, but after forming the desired shapes, heating is applied at about 200 C. for approximately 15 minutes, to completely decompose the tetraethyllead present.

Example VI When the procedures of the foregoing examples are repeated, but substituting comparable quantities of tetramethy-l lead, dimethyldiethyl lead, tetraisopropyl lead, and other organolead compounds, comparable results are achieved.

From the foregoing description and examples it will be seen that the principles of the present process are adaptable for a variety of embodiments. Thus, instead of the particle size distribution employed in Examples II, IV and V, a screened fraction of particles, passing a mesh screen and being retained on a N0. 200 screen, will result in ultimate shapes having somewhat higher density, and in addition, appreciably greater tensile strength and stillness. On the other hand, when the ultimate work shape desired is a relatively porous type material, it would be found highly advantageous to employed a screened fraction of a relatively coarse proportion. Illustratively, a desirable fraction for such purposes is a fraction passing a No. 10 US. screen and retained on a No. 25 screen. For producing thin sections of smaller porous size, a screen fraction passing a No. 25 screen and retained on a No. 100 screen is desirable.

As previously noted, a principal object of the present invention is the provision of a new and novel form of lead, having a high degree of porosity, and the process whereby such porosity can be generated and in addition an extremely fine form of lead deposited in the interstices or channel forming the pores. As previously described, this is accomplished by appropriate control of the quantity of organolead compound retained interspersed in the solid shape after forming and the controlled decomposition of said interspersed component. Although the lead organo compounds employed in the process are quite dense chemicals, nevertheless it is found that the relative densities thereof, contrasted to the density of the essentially lead metal forming the solid shape, is such that relatively small percentages can provide a respectable void or pore volume. Thus, in the typical system of lead powder and tetraethyllead, in a shape having no gas filled voids, and consisting essentially of 99 percent lead and 1 percent tetraethyllead, the latter component occupies about seven volume percent of the volume of the shape. Similarly, with two, three, and four weight percent concentrations of tetraethyllead, the volume occupancy would be 13, 18.8, and 23.7 volume percent respectively. As previously noted, the disposition of this component can be accomplished by chemical reaction, which results, usually, in deposition of at least a portion in the pores or interstices. Alternatively, and preferably, the solid shape is thermally treated resulting in a thermal decomposition of the lead organo component, accompanied by, if desired, removal of some portion as a vapor without change. Even when the lead organo component is entirely decomposed in situ, leaving a residual deposited lead portion from the molecule in place, the pore volume is not significantly changed. Thus, in the system, consisting essentially of 98 percent lead and 2 percent tetraethyllead, the thermal decomposition of all of the tetraethyllead will change the pore volume to only 12 percent of voids or a. reduction in pore volume of only 1 percent. Since the additional establishment of 1 percent lead volume in such a shape is in a form of microscopically or molecularly deposited lead, it is readily seen that an extremely high, active surface coating is applied in the pore channels. This form or product is very effective in filtering gases or liquid materials.

It will further be apparent that the degree of porosity, and the sizes of the apertures or pores of a formed shape according to the present invention, will be effected by the particle size distribution of the initial lead powder, the absolute particle size range, and the geometrical configuration of the individual particles. It will be un derstood that, if the particles were absolutely ideal spheres of constant diameter in a particular batch, and if said particles were oriented in a standard and uniform disposition, then the percent of void volume would be a constant regardless of the size of the particles. Of course, this situation is never achieved. Even if these were the facts, for larger particle sizes, the sizes of the pores or openings established in the ultimate shape would increase with increase in particle size. In actual practice, this effect is encountered, viz., upon increase in average particle size, the sizes of the pores established in the ultimate pieces are increased. Further, the sizes of pores are decreased with an increase in manipulative pressure in forming solid shape, prior to decomposition and removal of the lead organo liquid component. In addition, since in the actual powders employed in forming the shapes of the present invention, a statistical distribution is encountered, or even when a screened fraction is employed, there is a distribution of particle sizes, in practice, then, when the particles are in a larger size range, slightly higher percentages of voids exist, and some of the voids may be occupied actually by gas rather than fully by the lead organo compounds. In the other direction, when the average particle sizes are small, or for example when a screened fraction such as that passing a 200 mesh screen and retained on a No. 325 screen is employed, it is found that in addition to the actual pore openings being appreciably smaller, that the percent of void volume established after decomposition of the liquid lead organo compound is lower for a given set of conditions than for larger average particle sizes. From the foregoing considerations, it is quite apparent that a large number of attributes of the ultimate porous shape can be readily controlled by means of mechanical forming pressure, and by the technique of removing the liquid lead organo compound, and by control of the sizes of the lead powders employed for the process.

The precise temperature required for operation when a lead organo compound is to be eliminated by thermal decomposition will, of course, be determined, in part, by the particular identity of the organometallic liquid involved. In the case of the lead tetraalkyl compounds, in which all the alkyl groups are identical, for example, tetraethyllead, a temperature of above about 127 C. is required. Actually, in most cases an appreciably higher temperature is desirable or necessary, because the presence of substantial quantities of solid materials and nOnlead components tends to increase the temperature at which thermal decomposition can be effected. Thus, as a practical matter, a temperature of above 150 and up to about 300 C. is normally preferred, a temperature of the order of 150 to 250 being especially preferred in most cases. It will be further apparent that, to accomplish the particular function of eliminating the lead organo component the temperature of treatment should be below the melting point of lead metal, of about 327 C. In fact, treatment of a formed shape at a temperature approaching 300 0., say, has been found to effect the 0 physical properties of the shape with respect to the ductility and elongation before rupture.

In operations wherein the lead powder system con tains not only a lead liquid organo compound but also an aqueous phase, a temperature of above at least C. is necessary to fully eliminate the aqueous component from the resultant shape.

The pressures of operation are not highly critical, and will be selected and varied according to the technique of forming applied, the type of particle size distribution initially present, and the desired ultimate properties. When direct pressure in a mold is employed as the forming operation, a pressure of at least about 3,000 pounds per square inch is essential, and normally pressures above this level, particularly of the order of 5,000 up to about 20,000 pounds per square inch, are desired. Lower pressures can be employed for a given degree of volume reduction in procuring thinner-section shapes, than are required for thick section shapes. Further, when the shape to be produced is desired as essentially homogeneous and nonporous, pressures in the high range of 15 to about 30,000 pounds are sometimes employed. It will be understood that the pressures actually applied in certain types of forming operations are difficult to express. This is particularly true in the case of a rolling operation wherein a localized line contact can result in quite high local pressures.

As previously indicated and shown in the examples, the actual weight concentration of the organolead component present in the finished shape depends upon the severity of initial treatment and the initial particle size distribution. The organolead can be present in proportions of about /2 percent up to and in some unusual instances, as high as 10 weight percent. Normally, the most common range is from about 1 to about 3 percent organolead compound. When no voids are desired, the organolead present interspersed in the system should be in the range of about one-half to about 1.5 percent of the total weight. It will be recalled, as explained above, that even these relatively minor concentrations of the lead organo compound can be responsible for a significant volume in the heterogeneous formed shape, prior to decomposition. However, when the volume percent is 15 percent or lower, and the appropriate pressures of 15,000 pounds or above are applied, although some porosity is present, if the sectional thickness of the shape formed is inch or greater, impermeability can be achieved for such desired purposes. Alternatively expressed, when the forming operation results in a sectionthickness reduction of at least about one-half, and, preferably, at least three-fourths, then an impervious stock shape can be achieved.

The lead powder-charge stock systems frequently contain minor components other than the necessary lead organo compounds. The concentration of identity of such components varies with the preparatory history of the subdivided lead. In the case of lead which has been prepared by mechanical cutting operations, as for example, by milling with a multi-tooth cutter under an inert gas, very few extraneous component compounds will be present. On the other hand, when the lead is prepared by melting and atomizing by spraying and jetting with an air stream, a respectable concentration of lead oxide component will be present. When the lead has been exposed to contact with non-distilled water, frequently the lead contains minor concentrations of a lead carbonate or a lead carbonate-oxide complex. When the preparatory history of the lead powder has included a chemical reaction, for example, a reaction of a sodium lead alloy with an alkyl chloride, the lead powder will frequently contain minute quantities of lead halide and alkali metal halides such as sodium chlorides. Special treatment can be provided, when desired, to virtually eliminate the presence of such components from the charge stock. These special treatments will include leaching with water to dissolve any alkali metal halide. A dilurte acid Wash is sometimes used. The supplemental purification operations are usually not required, and actually, in some instances should be avoided. It is frequently found that the presence of minor contaminants or impurities actually contribute to the physical strength of the ultimate stock shapes. The reason for this is not fully understood, but it is theorized that minute or micro-molecular crystals of the impurities are lodged between minute crystals of the lead proper and tend to key the lead crystals or grains in the ultimate shapes and prevent slippage along grain surfaces Which results upon deformation of the shape.

The formed shapes produced by the present process find utility in many different applications. In those embodiments producing a virtually homogeneous and impervious shape, forms such as angles, channels, strips, rods, and \the like are readily produced. These can be employed as lead burning rods, for fabrication of construction shapes, or the like. An additional outlet for this product is flashing materials for roofing purposes, or flashing shapes in masonry work. The thin section pervious plate forms which can be produced by certain embodiments of the process can be employed as filter septums for filtration of certain noxious gases. One highly desirable function of such forms is as filter septums for gas streams containing minor quantities of radioactive dusts. The filter septum can not only remove from the flowing gas streams such dusts, but concurrently prevents the transmission of the radioactive energy emitted therefrom.

Having fully described the invention and the several embodiments thereof, what is claimed is:

1. Process for making lead stock shapes comprising mixing comminuted lead solids with a lead tetraorgano liquid in the proportions of from about 1 to about weight percent, applying pressure to the so-formed mixture, the pressure being insuflicient to separate more than a fraction of said lead tetraorgano liquid, and resulting in a solid shape containing a portion of the lead tetraorgano liquid distributed therein, and then heating the so-formed shape at an elevated temperature for a time suflicient to thermally decompose the said lead tetraorgano liquid to gaseous decomposition products and it) lead, and vaporize said gases from the shape and deposit at least a part of the lead therefrom in the spaces occupied by said lead tetraorgano liquid.

2. The process for making lead stock shapes comprising reacting an alloy of lead with a reactive metal with an alkylating agent and forming a reaction mixture including a lead tetraalkyl compound, an inorganic salt of the reactive metal and finely divided lead, then separating major portions of the lead tetraalkyl and the inorganic salt and establishing thereby a mixture comprising subdivided lead and minor portions of lead tetraalkyl admixed therewith, then mechanically forming said mixture under pressure conditions separating only a portion of the lead tetraalkyl, thereby providing a solid shape having minor quantities of the lead tetraalkyl interspersed therein, then thermally decomposing the said minor quantities of lead tetraalkyl into gaseous decomposition products and lead, vaporizing from the said shape the gaseous products and depositing at least a part of the lead therefrom in the spaces occupied by said lead tetraalkyl.

3. The process for making lead stock shapes comprising mechanically forming a shape from a high lead solids mixture, said mixture consisting essentially of lead and minor quantities of a lead rtet-raorgano compound, said shape having the said lead tetraorgano compound distributed therein, and then heating said shape at a temperature below the melting point of lead but sufiicient to decompose the said lead tetraorgano compound into gaseous decomposition products and lead, vaporizing from said shape the gaseous products, and depositing at least part of the lead from the lead tetraorgano compound in said shape.

References Cited in the file of this patent UNITED STATES PATENTS Gurnick May 31, 1955 Hobbs Mar. 27, 1956 OTHER REFERENCES 

1. PROCESS FOR MAKING LEAD STOCK SHAPE COMPRISING MIXING COMMINUTED LEAD SOLIDS WITH A LEAD TETRAORGANO LIQUID IN THE PROPORTIONS OF FROM ABOUT 1 TO ABOUT 10 WEIGHT PERCENT, APPLYNG PRESSURE TO THE SO-FORMED MIXTURE, THE PRESSURE BEING INSUFFICIENT TO SEPARATE MORE THAN A FRACTION OF SAID LEAD TETRAOGANO LIQUID, AND RESULTING IN A SOLID SHAPE CONTAINING A PROTION OF THE LEAD TETRAORGANO LIQUID DISTRIBUTED THEREIN, AND THEN HEATING THE SO-FORMED SHAPE AT AN ELEVETED TEMPERATURE FOR A TIME SUFFICIENT TO THERMALLY DECOMPOSE THE SAID LEAD TETRAORGANO LIQUID TO GASEOUS DECOMPOSITION PRODUCTS AND LEAD, AND VAPORIZE SAID GASES FROM THE SHAPE AND DEPOSIT AT LEAST A PART OF THE THEREFROM IN THE SPACES OCCUPIED BY LEAD TERTRAORGANO LIQUID. 